This invention relates to production of complex three-dimensional simulated stained glass objects from plastic materials.
An example of a simulated stained glass object which is made possible by the invention is a replica of the well-known Tiffany lamp shade which, in reality, is comprised of stained glass panes joined together with a low melting point metal such as lead solder. The method may be used to make simulated stained glass objects for advertising displays or decorative fixtures or furniture as further examples.
Production of substantially flat simulated stained glass panes has been achieved in the prior art as in U.S. Pat. No. 4,016,235. The method disclosed in this patent is suitable for making planar or two-dimensional simulated stained glass objects, such as window panes, where the only departure from the entire object lying in a single plane is the small relief that is required to simulate the lead joints between the facets corresponding with the glass chips in real stained glass panels as well as the texture typical of stained glass. The method of this patent involves printing a variously colored pattern of simulated stained glass facets and darkened simulated lead joints between them on a thin sheet of resin that is suitable for hot vacuum forming. The sheet is put in a mold cavity which has grooves corresponding with the pattern of the lead joints. A vacuum is drawn between one surface of the plastic sheet and the mold surface which has the grooves. A hot back-up layer of resin is then injected in the mold so as to force the thin printed sheet against the grooved die for producing an object which is essentially planar but has the necessary relief corresponding with the lead joints and glass texture. The thin printed resin sheet is not preformed before being placed in the injection mold. All forming is done in the injection mold under the influence of the high temperature and pressure of the injected resin. This method is not suitable for making the simulated stained glass objects which are grossly nonplanar to the extent of being hemispherical, or even spherical, as can be produced by the new method disclosed herein.
U.S. Pat. No. 3,122,598 is another prior art example of a method for making a decorated plastic or resin article such as a dinner plate which is basically two-dimensional as compared with the more pronounced third or depth dimension which is achievable with the new method disclosed herein. In this patent, the decoration or artwork is printed on a resin sheet that is quite thin. The sheet is then preformed to a limited extent by known vacuum or pressure methods to preshape it as required for the top surface of the plate. The preliminarily preformed sheet is then placed in a mold cavity, defined by spaced apart opposed mold faces, and hot resin is injected behind the sheet to form a base or substrate for the plate. This method is satisfactory for cases where the printed or decorative sheet does not undergo substantial deforming during the preforming process for, if it did, the decoration would be markedly distorted in the final product.
The problem of obtaining good registry between areas on the preformed object having relief with complementarily shaped recesses in the mold cavity is more acute when molding three-dimensional objects as contemplated by the invention than is the case where substantially planar objects are being molded as in the prior art. Insofar as is known, satisfactory molding of complex three-dimensional resin replicas of stained glass objects has not been achieved heretofore.